P-phenylenediamine stabilizers for elastomers and compositions containing the same



E. E. STAHLY Dec. 29, 1964 P-PHENYLENEDIAMINE STABILIZERS FOR ELASTOMERAND COMPOSITIONS CONTAINING THE SAME 4 Sheets-Sheet 1 Filed Aug. 151.l1956 2.7mm /v O O O O Q N sNouolw Nl Hidao avec 03n'lvA v INVENTOR ELDQNE. STA HLY BYjwLu/Z ATTORNEYS E. E. STAHLY ENEDIAMINE ST Dec. 29, 1964 3163 616 P-PHENYL ABILIZERS FOR ELAsToMERs AND coMPosI'rIoNs CONTAININGTHE SAME 4 Sheets-Sheet 2 Filed Aug. 3l. 1956 INVENTOR.

ELDON E. STAHLY O O O O l0 N (SNOHOIW) H LdSG )'IOVHO :IO EVVIVA V O O iATTORNEYS Dec. 29, 1964 E. E. STAHLY 3,163,615

P-PHENYLENEDIAMINE STABILIZERS FOR`ELASTOMERS AND COMPOSITIONSCONTAINING THE SAME Filed Aug. 51, 1956 4 Sheets-Sheet 3 VNGcI SlHVdATTORNEYS E. E. STAHLY Dec. 29, 1964 3 163 61 P-PHENYLENEDIAMINEsTABILIzERs FOR ELASTOMERS 6 AND COMPOSITIONS coNTAINING THE: SAME 4Sheets-Sheet 4 Filed Aug. 3l, 1956 OO OOM 00N OO. Om On ON O O XVM N l:IdVHVd SlHVd INVENTOR. ELDON E. STAHLY ATTORNEYS 3 163 616P-PHENYLENEDIAMEE STABRZERS FOR ELAS- TMERS AND COR/WGSHTIONS CONTAININGTHE SAME Eldon E. Stahly, Birmingham, Mich., assigner, by direct` andmesne assignments, of three-fourths to @liver W. Burke, Jr., GrossePointe, Mich., and one-fourth to Eastman Kodak Company, Rochester, N.Y.,a corporation of New Jersey Filed Aug. 31, 1956, Ser. No. 607,318 8Claims. (Cl. 2Mb-28.5)

This` invention relates to new chemical compounds which are useful forinhibiting polymers such as elastomers and plastomers againstdeterioration :by oxidative attack, more particularly by ozone, and tostabilizerelastomer compositions containing the same.

It is well known that polymers such as elastomers, particularly thosecontaining residual unsaturation, tend to crack due to attack by ozone,and such crack-formation in elastomer articles progressively increaseswith time and causes failure in the intended usage of such items, e.g.,tires, sealing strips, insulating cables, windshield wipers, gaskets,etc. The more nearly saturated elastomers, such as butyl rubber, andcertain polar substituted unsaturated elastomers such as neoprene areper se lesssubject to cracking via ozone attack, but such elastomerswhen plasticized for many uses, e.g., for low temperature performance,become subject to cracking by ozone. Hence inapplication it is foundgenerally desirable to protect most known elastomers against ozoneattack.

Itis an object of this invention to provide a new class of organiccompounds which are highly effective for retarding and preventingentirely, for extended periods of time, the development of cracks, dueto ozone attack, in elastomer compositions in static usages. A furtherobject is to provide synergistic antiozonant compositions which displaythis same stabilizing effect against ozone and which do not developblooms of undesirable dark colors. A still further object is to provideuseful stabilized and protected vulcanized elastomer compositions whichretain the eifectiveness of the new stabilizers during dynamic usages ofthe elastomer compositions wherein temperatures of 100 C. are developed.Such new stabilizers are termed antiozonants herein.

It has now been found that excellent elastomer stabilizing properties,particularly against ozone attack, are possessed byN-alkyl-N'-phenyl-p-phenylenediamines in which the alkyl group containsfrom 1 to` 19 carbon atoms. Members of this class in which `the alkylgroup contains from l to 9 carbonsare especially effective. The for-mulaof these compounds may be' represented by @NHeOrHR in which R representsalkyl groups. R may be primary, secondary or tertiary alkyl groups;itmay be a branched or straight chain alkyl group, and it may besubstituted with aryl or cycloalkyl radicals. This class of newantiozonants includes the smaller more restricted class of compoundsfound useful as gasoline antioxidants and disclosed in U.S. patent2,734,808. -It is also called to attention in said U.S. patent thatdesirable gasoline antioxidants are not ipso facto good rubberstabilizers.

lCe

Therefore prior to this invention it was not predictable that this newclass of compounds would be effective antiozonants for rubber.

Several examples containing alkyl groups in thepreferred range of numberof carbon atoms are: N-phenyl- Nisopropyl-p-phenylenediamine,Nphenyl-N'sec-butyl yamine, N phenyl-N-Z-ethylheXyl-p-phenylenediamine,N phenyl-N'1-ethyl 3 methylpentyl-p-phenylenediamine, N phenyl-N(l-isobutylisoamyl)-p-phenylenediamine, NphenylN-1-phenylethyl pphenylenediamine and N phenyl-Nbenzyl-p-phenylenediamine. Furtherexamples of members of this class of substituted p-phenylenediaminescontaining an N-phenyl group which are useful as antiozonants are thefollowing derivatives thereof: Nmethyl, Nethyl-, Nisobutyl, N'tertbutyl,N'2 amyl, N'isoarnyl, N1,amyl, N(l,3dimethylbutyl), N 1 methylhexyl,N(l-methyloctyl), N1methyl decyl, N4(2,6,8-trimethylnonyl), N2tridecyl,N2 pentadecyl, N2heptadecyl, and N 2 nonadecyl- Compounds of this typein which thealkyl group contains more than 19 carbon atoms possess someantiozonant properties but are less practical when used Aalone becauseof their greater molecular weight and lower migratability in theelastomer compositions incorporating them; but are useful in admixtureswith lower alkyl substituted vmembers of this class of compounds.

The lowest and intermediate members of this class of compounds areliquids freezing near room temperature while the higher members aresolids.v Nphenyl-Niso propyl-p-phenylenediamine has beenV madethe'subject of a divisional application since it is unique in `that itmelts.,

. tives are solids of lower melting point,(i.e., below roomtemperature). N-phenyl-N'-1phenylethyl is a solid of l00 C. M P. andNphenyl-N'tridecyl derivative isv a liquid andN-phenyl-Nf-Z-heptadecyl-p-phenylenediamine melts atabout C. Thederivatives containing octyl to nonadecyl alkyl groups distill in therange of 180 to 240 C. at less than 1 mm. mercury pressure. Thus the newclass of compounds disclosed by the present research comprises severaldistinct groups of more closely related compounds: (l) the uniqueN-phenyl-N isopropyl derivative which is the subject of a divisionalapplication and hence is not claimed herein, (2) the higher C4 to C19secondary and tertiary alkyl derivatives in which the secondary ortertiary alkyl substituent may be straight chain or branched, and may besubstituted with aryl or appropriate carbonyl compound, i.e., thealdehyde or ketone containing the desired number of carbon atoms. Thus,`2octanone, hydrogen and p-nitrosodiphenylamine are reacted in one stepat elevated temperatures (50 to C.) in the presence of catalysts such asplatinum, Raney nickel or copper oxide-chromium oxide combinations. Theymay also be prepared from the p-amino-dialessia phenylamine and thedialkyl sulfate containing the desired alkyl groups. Thus dimethylsulfate or diethyl sulfate can be reacted with p-amino-diphenylamine inan aqueous dioxane medium containing sodium hydroxide to provide theN-phenyl-Nmethylor N-phenylN-ethylp phenylenediamine respectively.

The antiozonants of this invention are effective in retarding andinhibiting the cracking of vulcanized elastomer items resulting fromozone attack. Unprotected elastomer compositions are quite rapidlydeteriorated via ozone attack, GR-S and natural rubber articles forexample in high ozone areas such as Los Angeles showing visual cracks ina matter of relatively few hours after being exposed to the atmosphere,whereas identical elastomer compositions into which 1 to 5 pts. of oneof the new class of antiozonants of this invention Vare incorporated donot crack under several years of exposure to the same atmosphere. Thepresent new antiozonant compositions are especially valuable forprotecting elastomer articles in dynamic usages wherein temperaturesabove 100 C. are attained. The compatibility of the new antiozonantswith rubber lis such that the migration characteristics are optimum formaintaining` a concentration of antiozonant at the surface of theelastomer article adequate to give protection against ozone, but aconcentration not so high that the antiozonant is rapidly depleted bysurface volatilization.

SYNERGISM This invention further provides synergistic antiozonantcompositions comprising mixtures of one or more of the newphenylenediamine derivatives with rubber antioxidants and/ or certainthioarnide derivatives, and waxes including parafnic andmicrocrystalline waxes and blends thereof. Thus a mixture comprisingfrom 1 to 9 parts of the new N-phenyl-N'alkylpphenylene diamineantiozonants, `to 9 parts of a rubber antioxidant (Table A) and/or athioamide (Table A), and 0 to 9 parts wax have been found eiective forprotecting elastomer compositions against ozone attack. Suchantioxidants, thioamides and waxes per se do not protect elastomers indynamic usage against ozone attack. l In such synergistic combinations,however, as little as 0.5 part of the substituted phenylenediamineantiozonants of the present invention per 100 parts of elastomercomposition demonstrate effective antiozone activity in rubbercompositions in dynamic uses.

In the accompanying drawings pertaining to representative embodiments ofthe invention: l

FIGS. 1 and 2 are illustrative charts drawn to simple coordinates, and

FIGS. 3 and 4 are illustrative charts drawn to seimilogarithmiccoordinates.

The antiozonants of this invention can. also serve as parent compoundsfor perparation of derivatives wherein at least one of the two`remaining hydrogens on the two nitrogens of R-NH-R-NHR are substitutedwith alkyl groups, nitroso, cyanohydrocarbon, poly(cyanoalkyl)polyamino,or acyl groups. Such derivatives of these parent compounds are part ofthe invention of the present inventor disclosed in,U.S. application,Ser. No. 606,767, filed August 28, 1956, and are not claimed herein.

Table A ANTIOXIDANTS SHOWING SYNERGISM WITH ANTIOZONANTS Amines:

6-ethoxy-2,2,4trimethyl1,2 dihydroquinoline (Santoflex AW)2,2,4-trimethyl-1,2-dihydroquinoline polymer (Agerite Resin D)Diphenylamine-acetone condensation products (BLE and Flectol H)1Phenyl-beta-naphthylamine (PBNA) Phenyl-alpha-naphthylamine (PANA orNeozone A)4 Table A-Continued Aniline-acetone condensation products 1Aniline-butyraldehyde condensation products 2 Dialpha-naphthylamineDi-beta-naphthylamine Phenylenediamine, o, m, and p-formsp,p-diaminodiphenylmethane (Tonox) p-aminodiphenylamine1,2-dianilinoethane (diphenylethylenediamine) o-tolidineN,Ndiphenyl-p-phenylenediamine (Perilectol X) NaphthylenediamineDi-p-methoxydiphenylamine (Thermoex) N,N-di-sec-hutyl-p-phenylenediamine(Tenamene 2) N,N-dibetanaphthyl p phenylenediamine (Agerite resin White)v N,Ndialpha-naphthyl-p-phenylenediarrrineTetraethylenepentaminopropionitrile Mixture of isopropoxydiphenylamine,diphenylphenylenediamine and phenyl-beta-naphthylamine (Agerite Hipar)Rosin Amine D 3 Y Dodecylamine 1N,N-tetramethylp,p'-di(aininophenyl)methaneN-dimethyl-p-phenylenediamine The cyanoalkylamines of R. G. Jennenscopending application, Ser. No. 556,432, tiled December 30, 1955, nowabandoned 4 Phenolic:

Parazone (p-phenylphenol) Santovar O (2,5-ditert-butyl hydroquinone)Hydroquinone Antioxidant 2246 (a p,pbispheno1, namely, 2,2methylene-bis(6-tert-butyl-p-cresol), produced by American Cyanamid CompanySantowhite Flakes (a dibutyl-phenol sulfide, namely, 4,4th.iobis(6-tertbutyl-m-cresol) produced by Monsanto Chemical Col Phosphites:

Triphenyl phosphite Tri(nonylphenyl)phosphite (Polygard) Aromaticesters:

Glycerol monosalicylate ester Dipropylene glycol monosalicylate esterThioamides:

T hioacetanilide Thiocarbanilide Thioacetamide DibenzylthioureaPhenylacetothiomorpholide The amounts of the new antiozonants and of thesynergistic antiozonant compositions containing these new antiozonantswhich are required to attain eifective protection of vulcanizedelastomer compounds against ozone attack is dependent to some extent onthe type of elastomer to be protected and its intended usage, but ingeneral will lie within the range of 2 to 5 parts per one hundred ofrubber. Where unusually high ozone concentrations are to be met, e.g.,in zones where ozone is generated by electric generators, even largeramounts may be required, even up to 10 pta/100 pts. elastomer. Therequired concentration is readily determined by prior ozone exposuretests of several preliminarily compounded samples containing varyingamounts of antiozonant or anti- 1 See College Outline Series, OrganicChemistry, by Degermg, Barnes & Noble, Inc., New York, 1951, page 268.

2'l'.hese anilne-butyraldehyde reaction products are commercial productsmarketed as Beutene (Naugatuck Chemical 0o.), Antox, and Accelerator 808SDH Pont Chemical oJb, and ik-32 (Monsanto Chemical Co. see alsofootnote a ove.

3Trade name for technical grade dehydroabetylamine. see CondensedChemical Dictionary, Reinhold Publ. Corp., NY. (lwpageio B1 P t tN 55orrespon ing e gian a en o. 3 700- corres ondin French Patent No.1,179,742. p g

ozonant composition under conditions simulating those of the intendedusage. Other materials such as dyes, .metal deactivators, andthe likemay be employed in conjunction with the antiozonants and synergisticantiozonant coinpositions of this invention.

PREPARATION AND TESTING PROCEDURES The procedures employed incompounding and testing the elastomer-amino-additive compositions forTables I, II and III herein was as follows: as control samples cold GR-Ssynthetic rubber (GR-S 1500 polymerized at 41 F. or GR-S 1600 which isthe saine except that 50 parts HAF carbon black are incorporated at thepolymer plant) was compounded and vulcanized according to best knowncommercial practice to obtain good aging properties. Then smiliarcompounds were prepared and vulcanized with my new antiozonants presentas additives. The re.- cipes employed, with Santollex AW for the controlcompounds replaced by varying quantities of the antiozonant as indicatedin the several'tables, were as follows:

Components: Tables l, Il, parts by Weight GR-S 1500 3 V100. HAF carbonblack 3 40 to 50. EPC carbon black 3 0 to 10. Zinc oxide 3. Stearic acid1 to 3. Phenylbetanaphthylamine (PBNA) 1 to 1.25. Circo Light Oil 1 2.5to 3.5. Para-Flux 2016 1 2.5 to 3.5. Sunproof, Heliozone, or Atlantic1115 wax 0 to 3.0.

Santocure (accelerator) 2 1.25. Sulfur 2.0. Additives As shown.

1Commercial plasticizing oils (see book entitled' CoinpoundingIngredients for Rubber, published 1947 by India Rubber World, New York.-N.Y.).

2Santocure is the trade naine for N-cyclohexyl-Zbenzothazole sulfenamde.

aGR-S' 1500 and the carbon blacks were occasionally'ie placed in Vthesecompounds by GR-S 1600 which is identical with GR-S 1500 except that italready contained 50 parts HAF black.

The recipes for other elastomers tested (Table III) are shown in thefollowing tabulation:

6 i The'various elastomer samples were cured at about 1000 p.s.i. in asteam heated press at 285 F. with curing times adjusted in the rangefrom 30 to 120 minutes, as required to obtain optimum tensile propertiesfor-each speciic compound. Samples of each of the cured stocks were heataged for 24 to 48 hours at 100 C. and were then subjected to ozoneexposures in both dynamic and static tests.

The examples in the tables herein are limited to sulfur curedvulcanizates, however, sulfurless curing systems for example withtetramethylthiuramidisulfide peroxide curing systems, such as withdicumyl peroxide; benzoquinone dioxirne; radiation curing systems usinga radiation source such as cobalt 60, metal oxide curing of acidelastomers as for example zinc oxide and butadiene-acrylic `acidcopolymers and similar curing systems can effectively be used withelastomers containing the antiozonants and synergistic antiozonantcompositions.

The dynamic ozone test was conducted on 3/2 -inch` dumbbell specimens ofthe vulcanizates. The exposure to ozone was carried out in analuminum-lined ozone cabinet where the concentration of ozone wasusually held at i5 p.p.h.rn. of air. This high ozone concentration isused (2515 p.p.h.m. is specified by ASTM Test D1149- 51T) Vtodemonstrate the protective effect of the antiozonants in a reasonablyshort time of evaluation and to approximate the atmospheric ozoneconcentrations reported at hgh altitudes attained by aircraft, and atground level in the Los Angeles area, to parts of New Mexico and Alaskaunder certain climatic conditions. Occasionally more highly acceleratedozone exposure tests were conducted by employing ozone concentrations ashigh as 150 p.p.h.m. With such high ozone concentrations much shortertimes are required to obtain Valid comparisons of the protective actionof the additves under test (e.g., Table I, Groups D and E). Each samplewas stretched and relaxed continuously at a rate of 30Vtimes per minutebetween 0 and 20% elongation on the total sample (0 to 28% on tne narrowportion suffering the elongation) to simulate conditions of dynamic useof the rubber. After each test, usually of 40 to 70 hours duration,aspecimen taken from the center part of the narrow part of the dumbbellwas placed under the microscope and the depth of the observed cracks wasmeasured. The depths of the Polybutadiene or Natural Rubber B utylGR-I-17 Neoprene Nitrile Type Rubber i Elastoinei (100 pts.) WHV HycarIngredients:

Philblack O Therniax (carbon black) Statex 125 (carbon black) MicronexW-6 (carbon black) Zinc oxide Stearic acid PB NA- BLE-25. Agerite ResinD A N eozone A rlP-QOB (plasticizer) b Dioctylphthalate (plasticizer)Pine Tar.-- Circo Light Oil Atlantic 1115 Wax Light Calcined MgO laltax(Benzothiazyl di lde nex e Methyl Tuads d n Sulfur Antiozonant andadditives l Oil-extended olyiner from sodium catalyst polymerizationcontains 20 to 25 parts petroleum oil extender. 1 Curing ingrelzlientsare defined in Compounding Ingredients for Rubber 2nd edition, publishedby India Rubber World, 1947.

b A high molecular weight polyether (Thiokol Corp). v Tetramethylthiuramnionosulde. d Tetramethylthiurain disulide.

For neoprene and butyl rubber the plasticization redeeper 50% of theobserved cracks were averaged, and

quired for low temperature performance results in nullifying a majorportion of the inherent ozone resistance of the polymer itself, andaccordingly the anitozonants of the present invention are useful in suchneoprene and butyl stocks.

this average was designated the A value and was taken as the index ofozone atack. With each experimental sample a control sample containingSvantoflex AW was simultaneously*subjected to the same dynamic ozonektest,

and the average crack depth A value was compared with the A value forthe crack depths of this cont-rol sample as a basis of evaluation.

In the Work on which this application and said copending application hasbeen based, it has been demonstrated that where antiozone protection isobtained in the dynamic tests, protection is also afforded in staticuse. The static tests run on both heat-aged and unaged samples showedthis to be true without exception. (The converse is not always true,e.g., some static protection is afforded by paran and microcrystallinewaxes, which are valueless for protection of rubber articles subjectedto dynamic usages.) Specimens for static testing were mounted inaccordance with ASTM procedure D 18-44, Method B. The mounted sampleswere placed in the ozone exposure cabinet wherein the ozoneconcentration was held at a concentration of 50i-5 at a temperature of40 C. In this static test the samples were observed periodically and thetime was measured to the appearance of the rst crack. Table I shows datafor typical static tests performed on examples according to theinvention of the present application wherein the tests were terminatedafter 6 weeks according to current practice of rubber testinglaboratories, since such static test data is merely coniirmative of dataobtained dynamically, further static ozone exposure test data for theantiozonants of the present application are omitted herefrom for thesake of brevity. It suffices to state that long continued tests showthat where virtual immunity against ozone was obtained with anantiozonant or a synergistic antiozonant composition in a 40 hour testat 50i5 p.ph.m. of ozone, static protection up to 6 months was obtainedat the same ozone concentration (i.e., 50 p.ph.m.) without appearance ofozone cracks. The Santoex AW controls showed severe cracking in the 40hour test and failed in about 100 hours or less under the same statictest conditions.

Similarly mounted panels of specimens (ASTM procedure D518-1l4) werealso statically tested in outdoor weather experiments in Florida(Miami), California (Los Angeles), and Michigan (Detroit). InCalifornia, Where highest concentrations of ozone occurred over the timeof the test (varied from 5 to 60 p.ph.m. dependent on weathervariations) up to six months outdoor exposure were required to developcracks (ASTM rating 4) in the samples containing -antiozonants orsynergistic antiozonan-t compositions. The Santoilew AW controls notonly cracked but failed in a month under simultaneous exposure. In theFlorida and Michigan tests the protected samples did not crack in aone-year test Whereas the control samples not ony cracked but failed inthe same test. The rating method for the static exposure tests is shownby the following tabulation.

Developments in static tests: Rating No developments of any kind 0Microscopic cracking V1- Fine visible cracking 2 Pronounced visiblecracking 3 Severe visible cracking V4 SYNERGISM In more detail, thesecond part of the present invention comprises the discoveries ofantiozonant compositions which rely on the action of synergisticantiozidants, paraffin and/or microcrystalline waxes in combination withspecific derivatives of p-phenylenediamines. When used in more than 3parts per 100 parts of elastomer the said derivatives ofp-phenylenediamine give virtual immunity to ozone attack per se.However, in combinations with Ycertain antiozidants it has been foundthat reduced amounts (e.g., 0.5 to 3.0 parts) of the said specificpphenylenediamine derivatives in combinations with 1.5 to 6 pts. totalof specific antioxidants serve to protect elastomers against ozonedeterioration, although the antioxidants by themselves do not impartozone resistance to the elastomer compounds, nor do the reduced amountsof l said speciicdiamino derivatives alone (i.e`., in the absence of thespecific antioxidants) show adequate protection of the elastomercompounds. Such admixed and/or interacted components which developantiozonant activity in protection of elastomers and plastomers aretermed herein synergistic compositions.

Thus I have made the `discovery that certain antioxidants identiedherein (see rFable A), themselves incapable of protecting elastomers andplastomers against ozone, have the property of greatly increasing theeffectiveness of reduced amounts of my specific antiozonants inelastomer and plastomer compositions. Such antioxidants I refer toherein as synergists Still another alternative interpretation of myinvention is that a small amount of a diamino antiozonant, which itselfcan impart ozone resistance to elastomer and plastomer compositionsincorporating said derivative in certain minimum amounts can developozone resistance in antioxidants when admixed therewith in less thansuch minimum amounts.

T he mechanism'of the action of such antioxidants in synergisticantiozonant compositions is not entirely understood. One possibleexplanation is that the diamino antiozonants themselves may ent-er tosome extent into the complex vulcanization reactions in the curing ofthey elastomer compositions, and that the synergistic antioxidant altersthe degree to which the diamino antiozonant so enters the vulcanizationreaction. Another possible explanation involves an alterationofmigratability characteristics of the antiozonant by the addition ofantioxidants. However, the exact mechanism is immaterial to the practiceof the invention which the subsequently discussed data servey toexemplify.

It is demonstrated that the wax component is an important component cfsome of the synergistic compositions. Thus virtual immunity resultedwith 2.5 parts Bil-86 (N-phenyl-N'-2-octyl-p-phenylenediamine), 1.25 pt.PENA and 0.5 part wax; whereas with the same amounts of 13R-86 and PBNAbut with no Wax present virtual immunity was not attained (FIG. 4).Similar synergistic elect of wax with other antiozonants of the presentinvention are apparent from the examples of th tables.

I have found that while paraflin and microcrystalline wax andcombinations thereof give some protection to static samples or"vulcanized elastomers no protection is afforded vulcanized elastomers indynamic usage. My findings confirm lohn O. Cole. In G. S. Whitbystreatise entitled Synthetic Rubber, published in 1954 by John Wiley &Sons, Inc., New York City, on page 541, Mr. Cole states, lt should bepointed out that, under dynamic exing, wax offersfno protection toeither GR-S or natural rubber (from the deterioration by ozone).

In contrast to this fact I have shown that waxes when i used with theantiozonants of this invention aot synergistically, that is, theyenhance theprotection value of Y the antiozonants.

OBSERVED RESULTS Many representative amino compounds, diamino compounds,polyamino compounds and derivatives thereof were tested in GR-S 1500wherein no adequate protection of vulcanized GR-S synthetic rubberagainst ozone attack was obtained either before or after the `GR-Ssynthetic rubber vulcanizate was subjected to accelerated aging atelevated temperatures. The results of these tests were listed in Table Iof copending joint application, S.N. 523,711, led I uly 22, 1955.However, they belong to one or more classes of materials known to haveantioxidant properties. Santoflex AW was found to be one of the best ofsuch antioxidants and since usage of said antioxidant was acceptable totire manufacturers in amounts up to 2 pts/100 of elastomers, 2 pts.Santoflex AW was used herein as a standard of comparison. Because of thenecessity of having separate controls for Veach group of samples testesamples containing Santotlex AW were tested with each group of samplescontaining other amino compounds to monitor the procedure and to giveassurance that the several results were valid for evaluating therelative eiectiveness of the several amino compounds for protection ofGR-S against ozone attack. 1

- Orthoand rneta-diamino aromatic compounds are re1- .atively inactiveas antiozonants, also certain compounds,

such as phenyl-alpha-naphthylamine derivatives, although goodantioxidants, are not good antiozonants.

A study of Table I of copending `joint U.S. application, Ser. No.523,711, filed July 22, 1955, is suicient to conrrn that mostrtypes ofamino-antioxidants are of little or no value in compounding elastomersto make ozone-resistant articles of use. Certain compounds show `someprotection against ozone in comparison with Santoex AW, but afterheat-agingV protection against ozone is negligible (e.g.,di-sec-butyl-p-phenylenediamine). Also certain diamino compounds such asbenzidine and 4- amino-diphenylamine protect against ozone, but also actas accelerators resulting in scorchy stocks not acceptable to theindustry.

STATIC OZONE TEST WITH TYPICAL EXAMPLES OF THE NEW OF ANTIOZONANTS INELASTOMERS It should also be called to attention that the GR-S 1500examples of the present invention contained from l to 1.25 parts ofeither phenyl-beta-naphthylamine (PBNA) or a diphenylamine-acetonecondensation product (BLE) in addition to the other additives shown,since such antioxidants were added at the polymerization plant.

Tables I, II and III demonstrate the effectiveness of the antiozonantsof the present invention of the formula R-NH-R-NHR" wherein Ris phenyl,R' is p-phenylene and R is alkyl or cyclohydrocarbon substituted alkyl,the total carbon count of the alkyl or so substituted alkyl containingfrom 1 to 19 carbon atoms. It will be noted that all are effective forstatic as Well as dynamic protection against ozone attack.

Table I shows protective action in GR-S and natural rubber resultingfrom incorporation of the` antiozonants of the present invention and thegreat improvement over the controls is readily apparent.

Table II shows similar protection afforded to GR-S by the newantiozonants in samples subjected to the dynamic ozone exposure test'and Table III shows the protection afforded other elastomers by the newantiozonants in samples subjected to the dynamic ozone test.

Tabla 1 CLASS [(5 pts/100 elastomers) 1.5 pts. parafinic wax added;505:5 p.ph.m. Ozone at 40 O., bent loop test (tests terminated at 1008hrs.)]

- Unaged, Aged (24 Hrs. Example Elastomer Add1tive, pts. per hundredelastomer Hrs. at 0 at 100 0.),

Rating Hrs. at 0 Rating Control (2 pts. Santoiiex AW) 5 2 N-Phenyl-N-isopropyl-p-phenylenediamine 1, 008 1, 000 N -Phenyl-N-2-octy1-p-pheny1ene diamine 1, 008 1 000 N-Phenyl-N1isobutyl3methylbutyl-p-phenylenediamine 1, 008 1, 000N-Phenyl-N-2-tridecyl-p-phenylenediamiue 1, 008 1, 000NPhenyl-N'-2-ethylhexy1-p-pheny1enediamine 1, 008 1, 000N-Phany1-N-1-phenylethyl-p-phenylenediamine 1, 008 1, G00N-Phenyl-N'-2-heptadecyl-p-phenylenediamine l, 008 1, 000NPheuyl-N'2-nonadecyl-p-phenylenediamine 960 960 Control (2 pts. SantoexAW plus 1 pt. PBNA). 10 2 N -PhenylN '-isopropyl-p-phenylenediamine 1,008 1, 008 N-Phenyl-Nbenzyl-p-phenylenediamine 1, 008 1, 008

Table II GR-S 1500 CONTAINING ANTIOZONANTS OF THE PRESENT INVENTION[Dynamic ozone exposure: 40 hrs. 50i5 p.ph.m. ozone: 40 C.; 30exes/minute-p-PD herein is used to designate paraphenylenediamine] AValue Crack Depth (Microns) Example Code Pts. Additive Btsvarafn UnagedAged 24 Hrs. at 100 C.

Group A:

1 Control-1 2.0 Santoflex AW-|1 pt. PBNA 0.5 240 460 2 4.0 SantoiiexAW-i-l pt. PBNA 0.5 75 400 2.0 Santoiex AW. 1. 5 225 500 None 0. 0 700700 1.5 N-Phenyl-Z-octyl-p-PD+15 pts. Tonox 1. 5 50 75 3.0N-Pheny1N2-octylp-PD 1. 5 30 35 5.0 NPhenylN-2octylp-PD 1. 5 25 0 5.0N-Phenyl-N-(1-isobutyl-methylbutyl) -p-PD 1. 5 30 25g.(Plhlenyl-Q-riieclggi-PD 1. 5 85 25 eny -n-oc y -pi]lj7i5tMirtureUof Zaryflenediunins )(2A)1 i 1 5 A 120 180 iopus2. ps.oamixure {15antioxidants from Table A 1 5 60 85 2.0 pts. of same mixture 2 ofantioxidants as used in A-ll 1. 5 225 240 2.0 Santoflex AW.- 1. 5 225460 2.0 N-PhenylN-2-octyl-p-PD+1.0 pt. stannous stearato 1. 5 30 50 3.0N-Phenyl-NZ-oetyl-p-PD 1. 5 50 s 40 (360) 2.0 N Phenyl-N2-octyl-p-PD 1.5 50 60 3.0 N-Phenyl-N(1ethyl3methylpenty1) -p-PD 1. 5 55 50 1.5 N-Phenyl-NQoctyl-p-PD plus 1.5 pts. N NDi2oetylp-PD 1. 5 50 95 1.oN-PheuyLN'eoecyrp-PD plus 1.o pr. N,N'Di2mry1p-PD plus 2.0 Santoex AW 1.5 65 90 3.0 N-Phenyl-N'-1-metl1ylheptyl-p-PD 1. 5 80 70 2.0N-Phenyl-N'-Lmethylheptyl-p-PD plus 1 pt. stannous stearate 0 45 85 3.0N-Pheny1-N(1ethyl3 methylpentyD-p-PD 0 45 15 2.0tN-P1enyl-N '-(1-ethyl-3methylpentyl)-p-PD plus 1.0 stannous O 100 60 s eara e. 3.0N-Phenyl-N-(1-ethyl-3-methylpentyD-p-PD 0 20 20 See footnotes at end oftable.

GR-S 1500 CONTAINING ANTIOZONANTS OF THE PRESENT INVENTION [Dynamicozone exposure: 40 hrs. 5015 p.ph.rn. ozone: 40 C.; 3Dfiexes/minute-p-PD herein is used to designate para-ph cnylenediamine] AValue Crack Depth (Microns) Example Code Pts. Additive Ptsarafn UnagedAged 24 1-1 rs.

at 100 C.

2.0 Santoflex AW 1. 5 200 320 5.0 N-Phenyl-N2ethylhexylp-PD 0 25 45 4.0N-Phenyl-2-oc'tyl-p-PD 1. 5 20 30 4.0 N -Phenyl-N-rsopropyl-pPD 0 0 04.0 N-Pherry1N -rsopropylp-PD l. 5 0 (l 4. N-Phenyl-Nrsopropyl-p-PD 1. 510 20 -Phenyl-Nethy1p-PD 0 10 l5 -PhenylNethyl-p-PD 1. 5 10 10-Pheuyl-N-1Sopropyl 0 30 0 -Phenyl-N'1sopropyl -PD 0 55 0-Pheuyl-Nsopropylp-PD 1. 5 45 35 Phenyl-N-iSopropylp-PD 0 100 250-PhenylN-methylp-PD 0 0 0 2 (B) Mixture of Antioxidants (1 pt. each)PBNA (Phenyl-beta-naphthylaruine) BLE-25 (diphenylamine-aeetonecondensation product) Polygard (tri(nonylphenybphosphrte) Santowhitecrystals (a dibutylphenol sulfide) 4-Aminodipl1enylaminep,p-Dirnethoxydipheuylamine Diphenylamine Tonox (p,pdianilinomethane)Agerito Resin D (Polymerized 2,2,4-tr1methyl-1,Z-dihydroquinollne)Hydroquinone t-Dodecylamine Sontoflex AW Dipropyleneglycol salicylateester 3 Parenthetic Value is crack depth obtained with sample aged 238hrs. at 100 C. which value is better than obtained for the control afteronly Table III ELASlOMERS OTHER THAN GR-S 1500, OONTAINING ANTIOZONANTSOF THE PRESENT INVENTION [Dynamic ozone exposure: 40 hrs. at 50;|;5p.p.h.m. ozone; 40 C.; 30 Ilexes per minute-p-PD herein is used todesignate para-phenylenediamine] "A ValueH Crack Depth (Microns) ExampleCode Elastomer Pts. Additive Ptsvlaralhn Unaged Aged 24 Hrs.

at 100 C.

Group D l M-19 Polybutadlene 0.25 NPhenylN2-oetylp-PD plus 1.75 pts. 1.5155 120 of a mixture of 7 other types of arylene diamines (A) 1 plus 2.0pts. mixed antioxidants (B).2 2 Control do 2.0 pts. mixed antioxidantsof preceding 1.5 365 4&0

' example.

Natural Rubber 6.0 Santolicx AW 1. 0 70 200 do 3.0N-Phenyl-N'2-oetylp-PD 1. 0 70 S0 3.0 NPhenyl-N'2tridecyl-p-PD 0 80 705.0 N-lhenylN-2ethylhexylpPD O 25 130 5.0 N-Phenyl-Nisopropylp-PD 0 0 01.0 N-Phenyl-N-isoprepyl-p-PD 0 65 S5 3.0 NPhenyl-NisopropylpPD 1. 0 2565 None. 0 280 340 3.0 N-PhenylNisopropyl-pPD 0 0 0 3.0NPhenyl-Nisopropy1p-PD 1. 5 0 0 2.0 N-PhenylN2-octy1p-PD plus 1 pt. 0 00 staunous stearate. 2.0 N-Phenyl-N-2octylp-PD plus 1 pt. 1.5 0 0stannous stearato.

Alfiu type GIR-S 1.0 PBNA 0 260 150 (79/21) 3 27 pts. oil extender. do5.0 N-Phenyl-N2octylp-PD 0 0 0 Hycar i014 1.5 BLE-25 1.5 7oo eoc do 5.05N-Phenyl-N'2-octyl-p-PD plus 1.5 BLE- 0 0 50 2 Y do 5.0N-Phenyl-N2-octyl-p-1D 0 30 35 Butyl Rubber None. 0 100 100 d5.01)1%\I?henyl-N-(1ethyl-3-mothylpentyD-p- 0 40 0 5.0N-.Plenyl-N-isopr'opyl-p-PD 0 20 5.0 N-Phcnyl-NisopropylpPD. 1.5 20 5.0NPheuyl-N'isopropylp-PD 0 0 0 2 (B) Mixture of Antioxidants (l pt..each) PBNA (Phenyl-beta-naphthylamme) BLE-25 (diphenylamine-acetonecondensation product) Polygnrd (tri(nonylphenyl)phosphite) Santowhitecrystals (a dihutylplrenol sulfide) 4-Amiuodiphenylaminep,p'-Dimethoxydiphenylamrne Diphenylamine Tonox (p,pdianilinometlrane)Agerite Resin D (Polymerized 2,2,4-trimcthyl-1,Qfdihydroquinoliuw2,5-Di-t-butylh ydroquinone Hydroquinone t-Dodecylamine Santolex AW fprocess was 79/21.

FIGURE 1 shows graphically the change in crack depth in relation tochangingconcentration for three new antiozonants wherein R contains 13,8 and 1,7"carbon atoms respectively. FIGURE 2 demonstrates the effectiverange of number otv carbon atoms in R.

depth A valuerepresents no improvement over the'Sant'oiex AW controlcompound simultaneously tested inV the dynamic ozoneexposure test. Theline VY represents the loss of immunity to ozone attackwhen the abilityof the antiozonant to migrate to Vthe surface is too low. Line X in suchdiagrams (as in copending U.S. application, Ser. No. 523,711) representsloss of immunity to ozone attack; in the present instance it approachesa car- "bon content of R equal to zero, at which point the draminebecomes :a monophenyl substituted p-phenylenediamine'. As pointed out inthe foregoing this compound is not acceptable for useV in` conventionalrubber compositions because ot its accelerating and scorchingtendencies, thus establishing the dotted line Z of FIGURE `2 as thelower limit (one carbon atom) for R in the range Y FIGURE 3; neither otthese antioxidants alone are effective for protecting against ozonecracking, yetin combination with as little as 0.5 pt. ofN-phenylN2octyl-pphenylenediarnine antiozonant these antioxidants formeda synergistic'mixture which imparts virtual immunity to unaged samples.When used alone 0.5 part of said antiozonant showed very litleprotection in comparison with the control compound. i

FIGURE V4 exemplifies synergism obtained with wax in combinations withthe antiozonants of the present invention. It is apparent that withincreasing amounts of parainic wax above 0.5 the synergistic improvementattributed to the `wax decreases, i.e., the maximum synergistic effectofthe wax is found for the lirst 0.5 pt. of

' wax, and most of the improvement attainable with wax is attained bythe addition of1.5 pts. wax.

FURTHER DISCUSSION .OF RESULTS `A iirst aspect of this invention hasdisclosed new antiozonants which per se in rubber containinginsignificant amountsv of antioxidants can protectV elastomers againstozone cracking. A second aspect has disclosed synergistic combinations-of such antiozonants with antioxidants and/or waxes. i

I have found that thequantity of antioxidant required to obtain'thesynergism varies with the antioxidants used. Most of the synergisticcombinations of antiozonants of this invention in combination withantioxidants such as` those examples of Table A contained at leastonepart lPENA. (addedat the, GR-S polymerization plants) in addition to theadded antioxidants. o

From the data obtained in dynamic ozone tests it appeared that 1l of theantioxidants of Table'A used only in 2 pts. per 100 pts. elastomer incombination with less than 3 pts. antiozonants of Table I-III per, 100pts. elastomer do not quite attain ettective protection in GR-S 1500compounds, viz:

BLE-25 Diphenylamine PBNA Rosin Amine D Flectol Hl l-naphthylamineAntioxidant 2246 o Virtual immunity is defined as the range of crackdepth A value below 50 microns. The line Vrepresenting 50() micronsycrack i is Dipropyle'ne glycol monosaiicylat'e ester Neozone A 1Paraz'one Polygard `some other synergist therewith. Y

With respect to the antiozonants of this invention,` the But it wasnoted from additional data that these l1 less actively synergisticantioxidants, when augmented by the 1.25 pts. of antioxidant present incommercial GRS;

did give effective synergistic protection of the elastomer comment asregards the insigniticance or" less than 1.5 parts total of antioxidants(that show significant synergism when used in greater than such amount)apply. The fact that paratiin wax alone is a better synergist thanmicrocrystalline wax has also been demonstrated. The data obtained withantiozonants of the present invention show the etiectiveness of theantiozonant perse, and the synergism therewith of antioxidants and/orwaxes. (See FIGURES 1, 2 and74.) In this connection, it will be notedthat (1) the effectiveness of wax as a synergist is developed to a majorextent ata wax content ot about 1.5 pts. wax with varying amounts ofthe'antiozonant and (2) the improvements in the aged samples from theinclusion of wax with the antiozonant generally parallel those in theunaged samples.

It has been further demonstrated that the beneficial elect of wax inoutdoor static tests is obtained. Thus, in static usages even in theabsence of synergisticvantioxidants, the time to irst cracking ofV GR-Ssamples containing 2.5 pts. of antiozonants of this invention can beconsiderably increased by inclusion of 1.5 pts. wax.

The antiozonants of the present invention tall Within the general classrepresented by formula wherein R is an arylcne radical selected from thegroup comprising phenylene and hydrocarbon substituted phenyleneradicals; R" is a radical selected fromV the group comprising alkyl andhydrocarbon substituted alkyl, including aralkyl (e.g., benzyl, 1- andZ-phenylethyl, phenyl (higher) alkyl, naphthylmethyl, naphthylethyl,tetrahydronaphthyl alkyl, etc.) and cycloalkyl substituted alkyl (eg,cyclohexylrnethyl, land 2-cyclohexylethyl, etc.); R is an aryl groupsuch as phenyl and alkyl substituted phenyl and cycloalkyl substitutedphenyl, and wherein the total number of carbon atoms yin the Rhydrocarbon substituent is in the range from 1 to 19 inclusive.

`While all compounds represented and defined by the above formula andlimitations given therewith per se show antiozone activity in highpolymer compositions, it is preferred to useN-phenyl-N-alkyl-p-phenylene diamines, N-phenyl-Naralkyl-p-phenylenediamines and N-phenyl-N- cyclohexylsubstituted alkyl-p-phenylenediamines, wherein the carbon count for theN substituent is 1 tof19, and which tall into three categories as aboveset out, only the second of which is claimed in this parent application.

Comparison of the results attained, mutually and with the controls,shows that various synthetic elastomers are protected against ozone byincorporation of one to iive parts of these antiozonants therein; andthe same considerations show that natural rubber is similarly protected,

vas well as polyisoprenes prepared synthetically by emulalessio l coldGR-S to sodium polymerized butadiene and butadiene-styrene mixtures,emulsion polymerized polybutadiene, butadiene-methylvinylpyridinecopolymer, butadiene-styrene-methacrylic acid copolymers, neoprene,butyl and Hycar l -rubber in that all of these elastomers have beensuccessfully protected against ozone by synergistic antiozonantcompositions of the present invention.

In addition to the examples given in the tables, copolymers of styreneand butadiene were prepared which contained small amounts ofcopolymerized carbonyl-containing monomers such -as methylvinylketone,crotonaldehyde or methylisopropenyl ketone and compounded with theantiozonants of this invention, and the results showed that theseantiozonants are useful as additives for these carbonyl containingelastomers.

These `and other elastomers may be employed as additives, e.g.,plasticizers for plastomer products, for which polar elastomers areusually selected. In such cases ozone deterioration of the elastomercomponent is prevented by the antiozonants of this invention.

The samples shown `in the tables cover 4the principal tyms ofelastomers, above described, but the range of polymers and combinationsprotected against ozone attack by the present antiozonants is notlimited thereto, as similar protection has been obtained with plastomercompositions containing elastomers such as butyl rubber, neoprene,polybutadiene, GR-S, acrylonitrile rubbers, etc., which elastomers perse show less susceptibility .to ozone attack.

Butyl rubber is known to be less susceptible to ozone attack than areGR-S elastomers. However, ozone cracking of butyl Vulcanizates is anindustrial problem for certain uses as evidenced by the study of D. C.Edwards and E. B. Storey, Transactions of the Institution of the RubberIndustry, pp. -69, vol. 31, No. 2, April 1955. l have found butyl rubberwhen plasticized with oiis as commercially practiced to be considerablyattacked by ozone. We have demonstrated that the anti-ozonants andsynergistic iantiozonant compositions of the presen-t invention whenappropriately compounded into butyl rubber are capable of protecting theresulting butyl vulcanizates against ozone attack. In like mannerplasticized neoprene compounds are protected :against ozone attack byappropriate use of antiozonants and antiozonant compositions of thisinvention.

The appropriate incorporation of the new antiozonant compositions, i.e.,combinations of the substituted phenylenediamines with aminoantioxidants and/ or waxes (and/ or metal salts such as certain metalfatty acid salts of said copending joint U.S. application, er. No.523,711) Vgives virtual immunity against much higher than ordinaryatmospheric concentrations of ozone, to elastomer compositions, evenwhen the same have been subjected to radical heat-aging, thus showingthat these antiozonant combinations are capable of protec-ting theproducts for long periods of `time under dynamic as well as staticconditions and at elevated temperatures.

The invention has further shown -that when the total carbons of 4thecompounds `are kept wi-thin designated ranges the antiozonants me highlyeffective in aged stocks, it being thus shown that lthe ranges arecritical for the protection of products subjected to high temperaturesresulting from dynamic usage or otherwise, but may be broadened lto someextent (e.g., a carbon count of say eight carbons less than theheat-aged ranges) and still be suitable for protection of static goodsnot subject to elevated temperatures or dynamic usages.

As also noted above, .the elastomers used in the examples of .the tablesherein generally contained antioxidant material capable of withstandingvulcanization, usually PBNA, but sometimes BLE. Such antioxidantmaterials afford no protection yagainst ozone attack of the principalproducts, nor do they effec-tively enable the other antioxidants ofTable A to do so. From the observed data, however, it is shown that incombination with it@ the new antiozonants, the PENA and other specific:antioxidant materials have a synergistic etlect enabling smallerquantities of the antiozonants of the present and the other specifiedinventions to effectively protect the products against ozone attack.

In general, from 1 yto 5 ptsqof the new diamine antiozonant per ofrubber in the absence of added antioxidants s adequate for practice ofthe present invention in protection of statically employed items(prepared from natural and synthetic rubbers) for practical periods oftime against deterioration due to ozone attack; 2.25 or more parts arepreferred for elastomer items in dynamic usages. ln synergisticcombinations, however, from 0.5 to 3 pts. ofthe substitutedp-phenylenediamines of this invention are su'licient to provide ozoneprotection for the elastomer compounds for both static and dynamicusage.

The amount of antiozonant compositions contain-ing synergisticantioxidants and/or waxes required to give ozone protection toelastomers varies with the type of antioxidants and metal salts (partIll of said copending joint invention) employed and `depends on whetherthe antioxidants and metal salts areused in combination or singly; ingeneral, for the practice of the present invention the total amount ofsynergistic additives varies from 1.25 to 6 pts. per hundred ofelastomer. The use of small amounts of waxes in rubber compoundstogether with antioxidants of course is recognized in the prior art.However, the appropriate combination of waxes with the antiozonants ofthe present invention, both with and without synergistic an-tioxidantsto develop synergistic antiozonant compositions, constitutes anunforeseeable and a valuable advance in the protection of elastomer andplastomer compositions against ozone cracking, in view of the fact thatwaxes were heretofore considered to be harmful for ozone resistance ofelastomers in dynamic usage.

The antiozonants and synergistic antiozonant compositions of the presentinvention have also been found to be etective in protection againstozone cracking of plastomers which have residual unsaturation or activehydrogens such as may be present in methylene or methinyl groups. Thus,resins or plastomer compositions cornprising polymers and copolymers ofvinylchloride, vinylacetate, alkylacrylates, etc., in combination withunsaturated polymer ingredients, are subject to attack by ozone, andsuch attack is avoided when the new antiozonants are present in suchcompositions.

In summarizing the parts of this invention it has been demonstratedthat: (1) antiozonants of the formula R-NH-R-NHR (as deiined above) whenused in from 1 to 5 pts. in 100 pts. elastomer and/ or plastomer protectthe elastomer compound against ozone attack; for protection againstunduly high concentrations of ozone larger amounts are eiectively used(e.g., up to 7.5 pts); (2) when the antiozonants of (1) are combinedwith appropriate quantities of antioxidants of the several classes ofantioxidants and/or waxes, synergistic antiozonant compositions areformed wherein reduced amounts of antiozonants will serve to protectelastomer compositions.

lt has further been demonstrated that the new antiozonants andsynergistic antiozonant compositions can be compounded with theelastomers in the Banbury mixer, 0n the rubber mill, or by incorporationin the elastomer latices either at the polymer plant or by the consumerat any time prior to coagulation and drying to produce compoundsstabilized against ozone.

The research has shown that the new compounds are valuable antiozonantsfor plastomers and resins as well as for natural and synthetic rubbersand are particularly useful antiozonants for tires and similar naturaland synthetic products (subject to ozone attack) which attain highoperating temperatures, such as those temperatures attained by heavyduty truck tires, and such temperatures may even rise to 300 F. in use.Antiozonants are heremaar in defined asn additive agents which protectthe polymeric` material, e.g., naturaland synthetic rubbers, againstdeterioration due to ozone attack. While serving as antiozonants the newcompositions also serve as antioxidants,

i.e., the new products of this invention protect against can too rapidlydisappear from the compounds incor-` porating them and ozone protectionwill thereafter be absent.

The present new class of compounds as herein dened, as well as eachsynergistic composition described herein is specific and differs ingeneral from other amines such as diarylamines, arylenediamines, andtheir derivatives, and mixtures with Vother types of antioxidants inthat other members of these general categories and their mixtures willnot effectively protect against attack by ozone as is demonstrated bythe research summarized hereinbefore.

These new antiozonant compositions have also been found effective inprotection of elastomer dispersions such as latices of natural rubber,GRS elastomers, neoprene, acrylonitrile copolymeric elastomers, and thelike which are to be used for coating and nlm-forming purposes, e.g.,for paper coatings, wall paints, etc. By incorporation of the newantiozonant compositions in the latices together with the vulcanizingingredients, the subsequently formed cured films therefromare'eiectively-protected against ozone cracking.

An antiozonant composition as used herein denotes any of the amineantiozonants represented by as herein defined, as well as each and everysynergistic composition described in the preceding discussion whethercontaining one or more of each class of synergists described, i.e.,waxes, certain metal salts, and the designated` classes of antioxidants.

Herein the term elastomer is employed to designate an elastic polymer ormacromolecule, whether a naturallyoccurring material or a syntheticpolymeric substance. Plastomer is defined as including both thermosetand thermoplastic high-molecular weight resinous and plastic materials.These definitions follow those used by Harry L. Fisher, Industrial andEngineering Chemistry, vol. 31, p. 942 (1939). n

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that minor modifications and changes may be madewithout departing from the essence of the invention. It is therefore tobe understood that the exemplary embodiments are illustrative and notrestrictive of the invention, the scope of which is deiined in theappended claims, and all modications that come within the meaning andrange of equivalency of the claims are intended to be included therein.

I claim:

1. The method `of protecting from ozone attack under both static anddynamic conditions rubbery material selected from the class consistingof natural rubber, polybutadiene, polychloroprene, butadiene-styrenerubbery copolymer, butadiene-acrylonitrile rubbery copolymer, and blendsof the foregoing, which consists essentially in incorporating into saidrubbery material, per 100 parts by weight thereof, 2.25 to 7.5 parts byweight of substituted p-arylene diamine represented by the formulaR-NH-R-NH- wherein R is a phenyl radical, R is a phenylene radical,

and R" is arradical selected from the class consisting of unsubstitutedand phenyl-substituted straight chain and wherein R is a phenyl radical,R' is a phenylene radical,` and R is a radical selected from the classconsisting ofl branched chain secondary and tertiary alkyl radicalscontaining from 4 to 19 carbon atoms.

2. Rubbery material selected from the class consisting of naturalrubber, polybutadiene, polych1oroprene`,`butadi ene-styrene rubberycopolymer, butadiene-acrylonitrile rubbery copolymer, and blends ot' theforegoing, and con-V taining inan amount eifective to protect it fromozone attack in `both static and dynamic usage, substituted p-arylenediamine'represented by the formula Y R--NH-RL-NH- l unsubstituted andVphenyl-substituted straight chain and branched chain secondaryandtertiary alkyl radicals containing from 4 to 19 carbon atoms, saideffective amount consisting of about 2.25 to 7.5 parts by weight per 100parts of the rubbery material.

3. A synergistic antiozonant composition for incorpora- V tion inrubbery material selected from lthe class consisting;

R--NH-R'-NH-R wherein R is a phenyl radical, R is a phenylene radical,

l and R isa radical selected from the class consisting of unsubstitutedand phenyl-substituted'straight `chain and branched chain secondary andtertiary alkyl radicals containing Vfrom 4 to 19 carbon atoms, withconversely fromV 2,2,4-trimethyl-1,2-dihydroquinoline polymer;

diphenylamine-acetone condensation products;

phenyl-beta-naphthylamine;

phenyl-alpha-naphthylamine;

aniline-acetone condensation products;

aniline-butyraldehyde condensation products;

di-alpha-naphthylamine;

di-beta-naphthylamine;

phenylenediamine,

p,p'-diaminodiphenylmethane;

p-aminodiphenylamine;

1,2-dianilinoethane;

o-tolidine;

N,Ndiphenyl-p-phenylenediamine;

naphthalenediamine;

di-p-methoxydiphenylamineg N,Ndi-beta-naphthyl-p-phenylenediamine;

N,N-di-beta-actetrahydronaphthyl-p-phenylenediamine;

tetraethylenepentaminopropionitrile;

mixture of isopropoxydiphenylamine, diphenylphenylenediamine andphenyl-beta-naphthylamine;

dehydroabietylamine;

dodecylamine-l N-dimethyl-p-phenylene diamine;

p-phenylphenol;

2,5-di-tert-butyl hydroquinone;

hydroquinone;

triphenyl phosphite;

tri(nonylphenyl) phosphite;

glycerol monosalicylate ester;

l dipropylene glycol monosalicylate ester; thioacetanilide;thiocarbonilide; thioacetamide; dibenzylthiourea;

phenylacetothiomorpllolde; and (iii) combinationsof the foregoing.

4. The method of protecting from ozone attack under both static anddynamic conditions rubbery material selected from the class consistingof natural rubber, polybutadiene, polychloroprene, butadiene-styrenerubbery copolymer, butadiene-acrylonitrile rubbery copolymer, and blendsof the foregoing, which consists essentially in incorporating into 100parts by weight of said rubbery copolymer an effective quantity in therange of about 2.25 to 7.5 parts by Weight of synergistic antiozonantcomposition according to claim 3, the quantity of said synergisticantiozonant composition employed in said range imparting to 100 parts byWeight of the unsaturated high polymer from about 3 parts by Weight ofthe antiozonant (a), when the composition comprises a small proportionof said synergistic material, to about 0.5 part by weight of theantiozonant (a) when the composition comprises a large proportion ofsaid synergis-tic material.

5. An ozone resistant combination containing 100 parts by weight ofrubbery material selected from the class consisting of natural rubber,polybutadiene, polychloroprene, butadiene-styrene rubbery copolymer,butadiene-acrylonitrile rubbery copolymer, and blends of the foregoing,and containing an effective quantity in the range of about 2.25 to 7.5parts by weight of synergistic antiozonant composition according toclaim 3, the quantity of said synergistic antiozonant compositionemployed in said range imparting to 100 parts by weight of the rubberymaterial from about 3 parts by weight of the antiozonant (a), when the20 composition comprises a small proportion of said synergisticmaterial, to about 0.5 part by Weight of said antiozonant (a) when saidcomposition comprises a large proportion of said synergistic material,and serving to pro tect'the combination from ozone attack under bothstatic and dynamic conditions.

6. A dioleiin polymer rubber vulcanizate comprising by Weight parts ofsaid rubber, .5-3 parts of an N-alkyl- N-phenyl-p-phenylenediaminewherein the said alkyl group contains from 2 to 9 carbon atoms and 1.5-6parts of microcrystalline wax.

7. A method of stabilizing a vulcanizable diene hydrocarbon rubberagainst cracking due to ozone which comprises incorporating in saidrubber from about 1% to about 5% by weight of N-(l-ethyl-3-methylpentyl)-N phenyl-p-phenylene diamine.

8. A diolen polymer rubber vulcanizate comprising by weight 100 parts ofsaid rubber, 0.5-3 parts of an N- alkyl-N-phenyl-p-phenylene-diaminewherein the said alkyl group contains from 2 to 9 carbon atoms and 0.5-6parts of microcrystalline wax.

References Cited in the iile of this patent UNITED STATES PATENTS2,166,223 Semon July 18, 1939 2,734,808 Biswell Feb. 14, 1956 2,822,395Dent Feb. 4, 1958 FOREIGN PATENTS 23,533 Australia July 17, 1935 520,097Great Britain Apr. 15, 1940 751,630 Great Britain Iuly 4, 1956 OTHERREFERENCES Shaw et al.: Antioxidants for GR-S Rubber, Rubber World, vol.130, August 1954, pp. 636-642.

1. THE METHOD OF PROTECTING FROM OZONE ATTACK UNDER BOTH STATIC ANDDYNAMIC CONDITIONS RUBBERY MATERIAL SELECTED FROM THE CLASS CONSISTINGOF NATURAL RUBBER, POLY BUTADIENE, POLYCHLOROPRENE, BUTADIENE-STYRENERUBBERY COPOLYMER, BUTADIENE-ACRYLONITRILE RUBBERY COPOLYMER, AND BLENDSOF THE FOREGOING, WHICH CONSISTS ESSENTIALLY IN INCORPORATING INTO SAIDRUBBERY MATERIAL, PER 100 PARTS BY WEIGHT THEREOF, 2.25 TO 7.5 PARTS BYWEIGHT OF SUBSTITUTED P-ARYLENE DIAMINE REPRESENTED BY THE FORMYLA